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Thorax:Radiological spaces:Pleural spaces
The pleura is a delicate fibrous membrane which is arranged in the form of a closed invaginated sac that encloses the lungs and lines the thoracic cavity. The pleura divides into: * visceral pleura * parietal pleura Parietal pleura: Lines the inner of the chest wall and separate in area by endothoracic fascia. It is named according to the site it lines. Costal portion extends along ribs and intercostal spaces; diaphragmatic portion covers the diaphragm; mediastinal portion covers the mediastinum * Blood Supply and Drainage ** Artery: related to adjacent chest wall (intercostal, internal mammary, diaphragmatic arteries) ** Vein: bronchial veins and azygos (diaphragmatic pleural drainage to inferior vena cava and brachiocephalic trunk) ** Lymph: intercostal, parasternal, diaphragmatic, and posterior mediastinal. * Innervation ** Intercostal nerves (costal and peripheral diaphragmatic pleura) and phrenic nerves (mediastinal and central diaphragmatic pleura) ** Irritation of costal or peripheral diaphragmatic pleura refers pain along intercostal nerves to thoracic or abdominal wall ** Irritation of mediastinal or central diaphragmatic pleura refers pain to lower neck and shoulder Visceral pleura: Covers the surface of the lung and extends into the fissures between its lobes. It is continuous with the parietal layer at the lung root. * Blood Supply and Drainage ** Artery: systemic bronchial artery ** Vein: pulmonary and bronchial veins ** Lymphatic drainage: deep pulmonary plexus within interlobar and peribronchial spaces toward hilum to the tracheobronchial nodes. * Innervation ** Visceral afferent nerves traveling along bronchial vessels; lacks pain fibers and autonomic only. Combined the thickness of the pleura and space is <0.5mm Function: Visceral pleura apposes and slides freely over parietal pleura during respiration. Giving traction during inspiration. Pleural space: * Potential space; normally contains 2-10 mL of fluid * Fluid production capacity, 100 mL/hr; fluid absorption capacity, 300 mL/hr * Fluid flux normally from parietal pleura capillaries to pleural space; absorbed by microscopic stomata in parietal pleura Pleural recesses Regions not occupied by the lung in the anterior and posterior regions of pleural cavities. These recesses provide potential spaces in which fluid can collect, they include; * costodiaphragmatic recesses is a potential space in the pleural cavity, at the posterior most tips of the cavity, located at the junction of the costal pleura and diaphragmatic pleura. It measures approximately 5 cm vertically, and extends from the eighth to the tenth rib along the mid-axillary line. * costomediastinal recesses FISSURES: * General Concepts ** Complete fissures extend from the lung surface to the hilum ** Incomplete fissures fail to extend to the hilum; allowparenchymal communication and collateral air drift between adjacent lobes * Major (Oblique) Fissures ** Originate posteriorly, near level of T5 vertebral body; left major fissure originates near T4 in 75% of individuals ** Terminate along anterior diaphragmatic pleural surface, 3-4 cm posterior to anterior chest wall ** Right major fissure separates right upper lobe and middle lobe from right lower lobe ** Left major fissure separates left upper lobe from left lower lobe ** Change in contour from upper portion (concave anterior aspect) to lower portion (convex anterior aspect); termed propeller-like morphology * Minor (Horizontal) Fissure ** Separates superior aspect of middle lobe from right upper lobe; incomplete in >80% of individuals ACCESSORY FISSURES * General Concepts ** Clefts of varying depth in outer surface of lung; occur in 22-32% of individuals * Azygos Fissure ** Right-sided; results from failure of normal migration of azygos vein to tracheobronchial angle ** Invaginated visceral and parietal pleura form fissure (four layers of pleura) in medial aspect of right lung apex (see "Lungs" section) * Left Minor Fissure ** Separates lingula from remainder of left upper lobe; frequency of 8-18% but rarely detected on PA chest radiography (frequency of 1.6%) * Superior Accessory Fissure ** Separates superior segment of lower lobe from basal segments; horizontal or oblique in orientation * Inferior Accessory Fissure ** Incompletely separates medial basal segment from rest of basal segments of lower lobe; right more common than left ** Frequency of 5-10% on chest radiographs, 16-21% of chest CT studies, and 30-50% of anatomic specimens